Steady state voltage instability assessment in a power system

With the increase of loading and exploitation of power transmission system and also due to the improved optimized operation, the problem of voltage stability and voltage collapse attracts more and more attention. The phenomenon of possible steady state voltage instability is creating serious concern among operators of large interconnected power systems. Maintaining adequate system voltage has become a major problem, as utilities are being forced to operate the system close to the thermal capability or steady state voltage stability limit. A voltage collapse can take place in power systems or subsystems quite abruptly, which requires improved continuous monitoring of the system state. There are different methods used to study the voltage collapse phenomenon, such as the Jacobian method, the simplified Jacobian method, the multiple load flow method and the voltage collapse proximity indicator method. It is proposed to modify the method of multiple load flow to obtain the weakest buses and the maximum injected powers for each bus. The method of voltage collapse proximity indicators is also simplified. These different methods are applied on a simple power system to study the problem of voltage-collapse, and a comparison is made between them with indicating the merits and demerits of each. (C) 1998 Elsevier Science Ltd. All rights reserved.